TYPO3 Core

We experienced the attached warnings shown in BE. After clearing all caches and in BE for example opening a content-element for editing the errors appeared. Problem boiled down to XML-file EXT:t3s_headerslider/pi1/locallang_csh.xml
Trying to shrink that XML-file as far as possible the error still persisted. I can't yet say why only this one file caused problems. Moving that file away the error was gone.

PHP Warning
PHP Warning: count() [function.count]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 95
PHP Warning
PHP Warning: TYPO3\CMS\Core\Localization\Parser\LocallangXmlParser::getParsedDataForElement() [typo3\cms\core\localization\parser\locallangxmlparser.getparseddataforelement]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 103
PHP Warning
PHP Warning: count() [function.count]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 95
PHP Warning
PHP Warning: TYPO3\CMS\Core\Localization\Parser\LocallangXmlParser::getParsedDataForElement() [typo3\cms\core\localization\parser\locallangxmlparser.getparseddataforelement]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 103
PHP Warning
PHP Warning: count() [function.count]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 95
PHP Warning
PHP Warning: TYPO3\CMS\Core\Localization\Parser\LocallangXmlParser::getParsedDataForElement() [typo3\cms\core\localization\parser\locallangxmlparser.getparseddataforelement]: Node no longer exists in /var/www/html/typo3/sysext/core/Classes/Localization/Parser/LocallangXmlParser.php line 103